Constraining Radiatively Inefficient Accretion Flows with Polarization

Abstract

The low-luminosity black hole Sgr A* provides a testbed for models of Radiatively Inefficient Accretion Flows (RIAFs). Recent sub-millimeter linear polarization measurements of Sgr A* have provided evidence that the electrons in the accretion flow are relativistic over a large range of radii. Here, we show that these high temperatures result in elliptical plasma normal modes. Thus, polarized millimeter and sub-millimeter radiation emitted within RIAFs will undergo generalized Faraday rotation, a cyclic conversion between linear and circular polarization. This effect will not depolarize the radiation even if the rotation measure is extremely high. Rather, the beam will take on the linear and circular polarization properties of the plasma normal modes. As a result, polarization measurements of Sgr A* in this frequency regime will constrain the temperature, density and magnetic profiles of RIAF models.

4 pages, 3 figures, accepted by ApJ Letters

References in corpus (21)

• On the Fate of Gas Accreting at a Low Rate onto a Black Hole
• Advection-Dominated Accretion: Self-Similarity and Bipolar Outflows
• Chandra X-ray Spectroscopic Imaging of Sgr A* and the Central Parsec of the Galaxy
• The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy's Central Black Hole: A Paradox of Youth
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• The Supermassive Black Hole at the Galactic Center
• Convection-Dominated Accretion Flows
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• Spectral Models of Advection-Dominated Accretion Flows with Winds
• Global MHD Simulation of the Inner Accretion Disk in a Pseudo-Newtonian Potential
• Interferometric Measurements of Variable 340 GHz Linear Polarization in Sagittarius A*
• Constraining the Accretion Rate Onto Sagittarius A* Using Linear Polarization
• Hybrid Thermal-Nonthermal Synchrotron Emission from Hot Accretion Flows
• Sgr A* Polarization: No ADAF, Low Accretion Rate, and Non-Thermal Synchrotron Emission
• Numerical Simulations of Convective Accretion Flows in Three Dimensions
• Circular Polarization of Radio Emission from Relativistic Jets
• Variable Linear Polarization from Sagittarius A*: Evidence for a Hot Turbulent Accretion Flow
• Circular polarization from stochastic synchrotron sources
• Sub-milliarcsecond Imaging of SgrA* and M87
• Properties of the Radio-Emitting Gas Around SgrA*

Cited by in corpus (13)

• First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
• Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity
• MHD Simulations of Accretion onto Sgr A*: Quiescent Fluctuations, Outbursts, and Quasi-Periodicity
• General relativistic polarized radiative transfer: building a dynamics-observations interface
• Modeling mm- to X-ray flare emission from SgrA*
• The Circular Polarization of Sagittarius A* at Submillimeter Wavelengths
• Faraday Conversion and Rotation In Uniformly Magnetized Relativistic Plasmas
• Black Hole Magnetic Fields and Their Imprint on Circular Polarization Images
• Propagation Effects in Magnetized Transrelativistic Plasmas
• Faraday Rotation in Global Accretion Disk Simulations: Implications for Sgr A*
• The Variability of Polarized Radiation from Sgr A*
• Gamma-ray emission from proton-proton interactions in hot accretion flows
• Modelling the time dependence of the TeV Gamma-ray source at the Galactic Centre